The present relates to novel triazolotriazinones, to processes for preparing them and to their use as medicaments, in particular as inhibitors of cGMP-metabolizing phosphodiesterases.
J. Heterocycl. Chem. (1993), 30(5), 1341-9, J. Heterocycl. Chem. (1984), 21(3), 697-9 and Nucleosides Nucleotides (1995), 14(7), 1601-12 describe 6-amino-triazolotriazinones which have an antiviral effect.
J. Med. Chem. (1986), 29(11), 2231-5 also describes 6-amino-triazolotriazinones as nucleoside analogs having an antitumor effect. Triazolotriazinones having the substituents described in the present invention and having an inhibitory effect against cGMP-metabolizing phosphodiesterases have not been disclosed.
The compounds according to the invention are potent inhibitors of cyclic guanosine 3xe2x80x2,5xe2x80x2-monophophate-metabolizing phosphodiesterases (cGMP -PDEs). In accordance with the nomenclature of Beavo and Reifsnyder (Trends in Pharmacol. Sci. 11, 150-155, 1990), these phosphodiesterases are the phosphodiesterase isoenzymes PDE-I, PDE-II and PDE-V.
An increase in the concentration of cGMP can lead to therapeutic, antiaggregatory, antithrombotic, antiproliferative, antivasospastic, vasodilatory, natriuretic and diuretic effects. It can exert an effect on the short-term or long-term modulation of vascular and cardiac inotropy, cardiac rhythm and stimulus conduction in the heart (J. C. Stoclet, T. Keravis, N. Komas and C. Kugnier, Exp. Opin. Invest. Drugs (1995), 4 (11), 1081-1100). Inhibition of the cGMP-PDEs can also strengthen erection. These compounds are therefore suitable for treating erectile dysfunctions.
The present invention now relates to triazolotriazinones of the general formula (I), 
in which
R1 represents straight-chain or branched alkyl having up to 6 carbon atoms or represents (C3-C8)-cycloalkyl,
R2 represents hydrogen or represents straight-chain or branched alkyl having up to 6 carbon atoms,
R3 and R4 are identical or different and represent hydrogen or (C1-C6)-alkoxy or represent (C1-C6)-alkyl which is optionally substituted, up to 3 times, identically or differently, by hydroxyl, (C1-C5)-alkoxy or phenoxy or by radicals of the formulae xe2x80x94Oxe2x80x94COxe2x80x94NR5R6, xe2x80x94NR7R8 or 
xe2x80x83in which
R5, R6, R7 and R8 are identical or different and denote hydrogen, (C1-C6)-alkyl or phenyl, or
R7 and R8, together with the nitrogen atom to which they are bonded, form a 5- to 6-membered, saturated heterocycle which can additionally contain a further heteroatom from the series S and O,
and/or (C1-C6)-alkyl is, for its part, optionally substituted by phenyl which is optionally substituted, up to 3 times, identically or differently, by hydroxyl, (C1-C6)-alkoxy or halogen or by (C1-C6)-alkyl which, for its part, is in turn substituted by hydroxyl or (C1-C6)-alkoxy, or phenyl is optionally substituted by radicals of the formulae xe2x80x94SO2xe2x80x94NR9R10 or xe2x80x94NR11R12, in which
R9, R10, R11 and R12 are identical or different and denote hydrogen, (C1-C6)-alkyl or phenyl, or
R11 and R12, together with the nitrogen atom to which they are bonded, form a 5- to 6-membered, saturated heterocycle which can additionally contain a further heteroatom from the series S and O, or
R3 represents hydrogen or (C1-C6)-alkyl, and
R4 represents radicals of the formula 
xe2x80x83or represents phenyl which is optionally substituted, up to 3 times, identically or differently, by halogen, (C1-C6)-alkoxy or hydroxyl or by a radical of the formula 
xe2x80x83or by (C1-C6)-alkyl which, for its part, can be substituted by hydroxyl or (C1-C6)-alkoxy, or
R3 and R4, together with the nitrogen atom to which they are bonded, form a radical of the formula 
xe2x80x83in which
R13 denotes hydrogen, (C1-C6)-alkoxycarbonyl, (C3-C6)-cycloalkyl, pyridyl, pyrimidyl or (C1-C6)-alkyl which is optionally substituted by hydroxyl,
R14 and R15 are identical or different and denote hydrogen, hydroxyl or (C1-C6)-alkyl which is optionally substituted by hydroxyl or by a radical of the formula xe2x80x94P(O)(OR18)(OR19), in which
R18 and R19 are identical or different and denote hydrogen or (C1-C6)-alkyl, or
R14 and R15 together form a radical of the formula xe2x95x90Nxe2x80x94OH,
R16 and R17 are identical or different and denote hydrogen or (C1-C6)-alkyl which is optionally substituted by hydroxyl,
and the salts, N-oxides and isomeric forms thereof.
The compounds according to the invention can exist in stereoisomeric forms which either relate to each other as image and mirror image (enantiomers) or which do not relate to each other as image and mirror image (diastereomers). The invention relates to both the enantiomers or diastereomers or their respective mixtures. The racemic forms, as well as the diastereomers, can be separated into the stereoisomerically uniform constituents in a known manner.
The substances according to the invention can also be present as salts. Within the context of the invention, preference is given to physiologically harmless salts.
Physiologically harmless salts can be salts of the compounds according to the invention with inorganic or organic acids. Preference is given to salts with inorganic acids, such as hydrochloric acid, hydrobromic acid, phosphoric acid or sulfuric acid, or salts with organic carboxylic or sulfonic acid, such as acetic acid, maleic acid, fumaric acid, malic acid, citric acid, tartaric acid, lactic acid or benzoic acid, or methanesulfonic acid, ethanesulfonic acid, phenylsulfonic acid, toluenesulfonic acid or naphthalenedisulfonic acid.
Physiologically harmless salts can equally well be metal or ammonium salts of the compounds according to the invention. Particular preference is given, for example, to sodium, potassium, magnesium or calcium salts, and also to ammonium salts which are derived from ammonia, or to organic amines, such as ethylamine, di- or triethylamine, di- or triethanolamine, dicyclohexylamine, dimethylaminoethanol, arginine, lysine, ethylenediamine or 2-phenylethylamine.
(C3-C8)-Cycloalkyl and/or (C3-C6)-cycloalkyl represents cyclopropyl, cyclopentyl, cyclobutyl, cyclohexyl, cycloheptyl or cyclooctyl. Those which may be mentioned as being preferred are: cyclopropyl, cyclopentyl and cyclohexyl.
(C1-C6)-Alkyl represents a straight-chain or branched alkyl radical having from 1 to 6 carbon atoms. Those which may be mentioned by way of example are: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl and n-hexyl. Preference is given to a straight-chain or branched alkyl radical having from 1 to 4 carbon atoms. Particular preference is given to a straight-chain or branched alkyl radical having from 1 to 3 carbon atoms.
(C1-C6)-Alkoxy represents a straight-chain or branched alkoxy radical having from 1 to 6 carbon atoms. Those which may be mentioned by way of example are: methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentoxy and n-hexoxy. Preference is given to a straight-chain or branched alkoxy radical having from 1 to 4 carbon atoms. Particular preference is given to a straight-chain or branched alkoxy radical having from 1 to 3 carbon atoms.
Within the context of the invention, (C1-C6)-alkoxycarbonyl represents a straight-chain or branched alkoxycarbonyl radical having from 1 to 6 carbon atoms. Those which may be mentioned by way of example are: methoxycarbonyl, ethoxycarbonyl, n-propoxycarbonyl, isopropoxycarbonyl and tert-butoxycarbonyl. Preference is given to a straight-chain or branched alkoxycarbonyl radical having from 1 to 4 carbon atoms. Particular preference is given to a straight-chain or branched alkoxycarbonyl radical having from 1 to 3 carbon atoms.
In general, halogen represents fluorine, chlorine, bromine and iodine. Preference is given to fluorine, chlorine and bromine. Particular preference is given to fluorine and chlorine.
A 5- to 6-membered aromatic heterocycle having up to 3 heteroatoms from the series S, O and/or N represents, for example, pyridyl, pyrimidyl, pyridazinyl, thienyl, furyl, pyrrolyl, thiazolyl, oxazolyl or imidazolyl. Preference is given to pyridyl, pyrimidyl, pyridazinyl, furyl and thienyl.
Preference is given to compounds according to the invention of the general formula (I), in which
R1 represents straight-chain or branched alkyl having up to 5 carbon atoms, or represents cyclopropyl, cyclopentyl or cyclohexyl,
R2 represents straight-chain or branched alkyl having up to 4 carbon atoms,
R3 and R4 are identical or different and represent hydrogen or methoxy or represent (C1-C5)-alkyl which is optionally substituted, up to 3 times, identically or differently, by hydroxyl, (C1-C4)-alkoxy or phenoxy or by groups of the formulae xe2x80x94Oxe2x80x94COxe2x80x94NR5R6, xe2x80x94NR7R8 or 
xe2x80x83in which
R5, R6, R7 and R8 are identical or different and denote hydrogen, (C1-C4)-alkyl or phenyl, or
R7 and R8, together with the nitrogen atom to which they are bonded, form a morpholine, piperidine or pyrrolidine ring,
and/or (C1-C5)-alkyl is, for its part, optionally substituted by phenyl which can be optionally substituted, up to 3 times, identically or differently, by hydroxyl or (C1-C4)-alkoxy or by (C1-C4)-alkyl which, for its part, is in turn substituted by hydroxyl or (C1-C4)-alkoxy, or phenyl is optionally substituted by radicals of the formulae xe2x80x94SO2xe2x80x94NR9R10 or xe2x80x94NR11R12, in which
R9, R10, R11 and R12 are identical or different and denote hydrogen, (C1-C4)-alkyl or phenyl, or
R11 and R12, together with the nitrogen atom to which they are bonded, form a morpholine, piperidine or pyrrolidine ring, or
R3 represents hydrogen or (C1-C4)-alkyl, and
R4 represents radicals of the formula 
xe2x80x83or represents phenyl which is optionally substituted, up to 3 times, identically or differently, by fluorine, (C1-C4)-alkoxy or hydroxyl, by a radical of the formula 
xe2x80x83or by (C1-C4)-alkyl which can, for its part, be substituted by hydroxyl or (C1-C3)-alkoxy, or
R3 and R4, together with the nitrogen atom to which they are bonded, form a radical of the formula 
xe2x80x83in which
R13 denotes hydrogen, (C1-C4)-alkoxycarbonyl, cyclopentyl, cyclohexyl, pyridyl, pyrimidyl or (C1-C5)-alkyl which is optionally substituted by hydroxyl,
R14 and R15 are identical or different and denote hydrogen or (C1-C5)-alkyl which is optionally substituted by hydroxyl or by a radical of the formula xe2x80x94P(O)(OR18)(OR19), in which
R18 and R19 are identical or different and denote hydrogen, methyl or ethyl, or
R14 and R15 together form a radical of the formula xe2x95x90Nxe2x80x94OH,
R16 and R17 are identical or different and denote hydrogen, hydroxyl or (C1-C3)-alkyl which is optionally substituted by hydroxyl,
and the salts, N-oxides and isomeric forms thereof.
Particular preference is given to compounds of the general formula (I), in which
R1 represents straight-chain or branched alkyl having up to 3 carbon atoms or represents cyclopentyl,
R2 represents straight-chain or branched alkyl having up to 3 carbon atoms,
R3 and R4 are identical or different and represent hydrogen or methoxy or represent (C1-C4)-alkyl which is optionally substituted, up to 3 times, identically or differently, by hydroxyl, (C1-C4)-alkoxy or phenoxy or by groups of the formulae xe2x80x94Oxe2x80x94COxe2x80x94NR5R6, xe2x80x94NR7R8 or 
xe2x80x83in which
R5, R6, R7 and R8 are identical or different and denote hydrogen, (C1-C3)-alkyl or phenyl, or
R7 and R8, together with the nitrogen atom to which they are bonded, form a morpholine, piperidine or pyrrolidine ring,
and/or (C1-C4)-alkyl is, for its part, optionally substituted by phenyl which is optionally substituted, up to 3 times, identically or differently, by hydroxyl, (C1-C3)-alkoxy or fluorine or by (C1-C3)-alkyl which is for its part in turn substituted by hydroxyl or (C1-C4)-alkoxy, or phenyl is optionally substituted by radicals of the formulae xe2x80x94SO2xe2x80x94NR9R10 or xe2x80x94NR11R12, in which
R9, R10, R11 and R12 are identical or different and denote hydrogen, (C1-C3)-alkyl or phenyl, or
R11 and R12, together with the nitrogen atom to which they are bonded, form a morpholine, piperidine or pyrrolidine ring, or
R3 represents hydrogen or methyl, and
R4 represents radicals of the formula 
xe2x80x83or represents phenyl which is optionally substituted, up to 3 times, identically or differently, by fluorine, methoxy or hydroxyl, by a radical of the formula 
xe2x80x83or by (C1-C4)-alkyl which, for its part, can be substituted by hydroxyl or methoxy or ethoxy, or
R3 and R4, together with the nitrogen atom to which they are bonded, form a radical of the formula 
xe2x80x83in which
R13 denotes hydrogen, (C1-C4)-alkoxycarbonyl, cyclopentyl, pyrimidyl or (C1-C3)-alkyl which is optionally substituted by hydroxyl,
R14 and R15 are identical or different and denote (C1-C3)-alkyl which is optionally substituted by hydroxyl or by a radical of the formula xe2x80x94P(O)(OR18)(OR19), in which
R18 and R19 denote ethyl, or
R14 and R15 together form a radical of the formula xe2x95x90Nxe2x80x94OH,
R16 and R17 are identical or different and denote hydrogen or (C1-C3)-alkyl which is optionally substituted by hydroxyl,
and the salts, N-oxides and isomeric forms thereof.
Very particular preference is given to the compounds which are listed in the following table: 
In addition, a process was found for preparing the compounds according to the invention of the general formula (I), which process is characterized in that compounds of the general formula (II) 
in which
R1 and R2 have the abovementioned meaning, is reacted with chlorosulfonic acid (ClSO3H), where appropriate in inert solvents and where appropriate in the presence of a base, to give the compounds of the general formula (III) 
xe2x80x83in which
R1 and R2 have the abovementioned meaning, and subsequently reacted with amines of the general formula (IV)
HNR3R4xe2x80x83xe2x80x83(IV),
xe2x80x83in which
R3 and R4 have the abovementioned meaning.
The process according to the invention can be explained, by way of example, by the following formula scheme: 
Solvents which are suitable for the individual steps are the customary organic solvents which are not altered under the reaction conditions. These solvents preferably include ethers, such as diethyl ether, dioxane, tetrahydrofuran or glycol dimethyl ether, or hydrocarbons, such as benzene, toluene, xylene, hexane, cyclohexane or petroleum fractions, or halogenohydrocarbons, such as dichloromethane, trichloromethane, tetrachloromethane, dichloroethane, trichloroethylene or chlorobenzene, or ethyl acetate, dimethylformamide, hexamethylphosphoric triamide, acetonitrile, acetone, dimethoxyethane or pyridine. It is likewise possible to use mixtures of the abovementioned solvents.
In general, the reaction temperatures can vary over a relatively wide range. In general, the temperatures employed are in a range of from xe2x88x9220xc2x0 C. to 200xc2x0 C., preferably of from 0xc2x0 C. to 70xc2x0 C.
In general, the process steps according to the invention are carried out under standard pressure. However, it is also possible to carry them out under positive pressure or under negative pressure (e.g. in a range from 0.5 to 5 bar).
The reactions can, for example, take place in a temperature range of from 0xc2x0 C. to room temperature and under standard pressure.
The compounds of the general formula (II) are novel and can be prepared by preparing, by means of reacting the compounds of the general formula (V)
R1xe2x80x94CO2Hxe2x80x83xe2x80x83(V),
in which
R1 has the abovementioned meaning, with thiocarbohydrazide 
xe2x80x83the compounds of the general formula (VI) 
xe2x80x83in which
R1 has the abovementioned meaning, then converting these compounds, by reaction with H2O2/CH3CO2H, into the compounds of the general formula (VII) 
xe2x80x83in which
R1 has the abovementioned meaning, and, in a further step, by means of reacting these compounds with compounds of the general formula (VIII) 
xe2x80x83in which
R2 has the abovementioned meaning, preparing the compounds of the general formula (IX) 
xe2x80x83in which
R1 and R2 have the abovementioned meaning, and subsequently converting these compounds, with diethyl carbonate, into compounds of the general formula (X) 
xe2x80x83in which
R1 and R2 have the abovementioned meaning, and finally cyclizing these compounds by heating to give the compounds of the general formula (II).
Solvents which are suitable for the individual steps are the customary organic solvents which are not altered under the reaction conditions. These solvents preferably include ethers, such as diethyl ether, dioxane, tetrahydrofuran or glycol dimethyl ether, or hydrocarbons, such as benzene, toluene, xylene, hexane, cyclohexane or petroleum fractions, or halogenohydrocarbons, such as dichloromethane, trichloromethane, tetrachloromethane, dichloroethane, trichloroethylene or chlorobenzene, or ethyl acetate, dimethylformamide, hexamethylphosphoric triamide, acetonitrile, acetone, dimethoxyethane or pyridine. It is likewise possible to use mixtures of the abovementioned solvents.
In general, the reaction temperatures can vary within a relatively wide range. In general, the temperatures employed are in a range from xe2x88x9220xc2x0 C. to 200xc2x0 C., preferably of from 0xc2x0 C. to 70xc2x0 C.
The process steps according to the invention are generally carried out under standard pressure. However it is also possible to carry them out under positive pressure or under negative pressure (e.g. in a range from 0.5 to 5 bar).
The reactions can, for example, take place in a temperature range of from 0xc2x0 C. to room temperature and under standard pressure.
The compounds of the general formulae (III), (IX) and (X) are novel and can be prepared, for example, as described above.
The compounds of the general formulae (IV), (V), (VI), (VII) and (VIII) are known and can be prepared using customary methods.
The compounds according to the invention of the general formula (I) exhibit a valuable pharmacological spectrum of activity which it was not possible to foresee.
They inhibit either one or several of the c-GMP-metabolizing phosphodiesterases (PDE I, PDE II and PDE V). This leads to an increase in c-GMP. The differing expression of the phosphodiesterases in different cells, tissues and organs, as well as the differing subcellular location of these enzymes, make it possible, in combination with the selective inhibitors according to the invention, to address the different cGMP-regulated processes selectively.
In addition, the compounds according to the invention augment the effect of substances such as EDRF (endothelium-derived relaxing factor) and ANP (atrial natriuretic peptide), of nitro vasodilators and all other substances which increase the concentration of the cGMP in another way than phosphodiesterase inhibitors.
The compounds according to the invention of the general formula (I) are therefore suitable for the prophylaxis and/or treatment of diseases in which an increase in the concentration of cGNT is therapeutic, i.e. diseases which are connected with cGNT-regulated processes (in English, usually simply termed cGMP-related diseases). These diseases include cardiovascular diseases, diseases of the urogenital system and cerebrovascular diseases.
Within the meaning of the present inventin, the term xe2x80x9ccardiovascular diseasesxe2x80x9d covers diseases such as high blood pressure, neuronal hypertension, stable and unstable angina, peripheral and cardiac vascular diseases, arrhythmias, thromboembolic diseases and ischemias such as myocardial infarction, stroke, transistory and ischemic attacks, angina pectoris and peripheral circulatory disturbances, and also prevention of restenoses following thrombolysis therapy, percutaneous transluminal angioplasty (PTA), percutaneous transluminal coronary angioplasties (PTCA) and bypass.
Furthermore, the compounds according to the invention of the general formula (I) can also have importance for cerebrovascular diseases. These include, for example, cerebral ischemia, stroke, reperfusion damage, brain trauma, edemas, cerebral thromboses, dementia and Alzheimer""s disease.
The relaxing effect on smooth musculature makes them suitable for treating disorders of the urogenital system such as prostate hypertrophy and incontinence and also, in particular, for treating erectile dysfunction and female sexual dysfunction.
Activity of the Phosphordiesterases (PDEs)
The cGMP-stimulatable PDE II, the cGMP-inhibitable PDE III and the cAMP-specific PDE IV were isolated either from porcine heart myocardium or from bovine heart myocardium. The Ca2+-calmodulin-stimulatable PDE I was isolated from porcine aorta, porcine brain or, preferably, from bovine aorta. The c-GMP-specific PDE V was obtained from porcine small intestine, porcine aorta, human blood platelets and, preferably, from bovine aorta. Purification was effected by means of anion exchange chromatography on Pharmacia MonoQR, essentially in accordance with the method described by M. Hoey and Miles D. Houslay, Biochemical Pharmacology, Vol. 40, 193-202 (1990) and C. Lugman et al. Biochemical Pharmacology Vol. 35 1743-1751 (1986).
The enzyme activity is determined in a 100 xcexcl test mixture, in 20 mM Tris/HCl buffer pH 7.5, which contains 5 mM MgCl2, 0.1 mg of bovine serum albumin/ml and either 800 Bq of 3HcAMP or 3HcGMP. The final concentration of the corresponding nucleotides is 10xe2x88x926 mol/l. The reaction is started by adding the enzyme, with the quantity of enzyme being measured such that approx. 50% of the substrate is transformed during the incubation time of 30 min. In order to test the cGMP-stimulatable PDE II, 3HcAMP is used as the substrate and 10xe2x88x926 mol of unlabeled cGMP/l is added to the mixture. In order to test the Ca2+-calmodulin-dependent PDE I, 1 xcexcM CaCl2 and 0,1 xcexcM calmodulin are additionally added to the reaction mixture. The reaction is stopped by adding 100 xcexcl of acetonitrile which contains 1 mM cAMP and 1 mM AMP. 100 xcexcl of the reaction mixture are separated by HPLC and the cleavage products are determined quantitatively online using a flow-through scintillation counter. The substance concentration at which the reaction rate is decreased by 50% is measured. The xe2x80x9cphosphodiesterase [3H] cAMP-SPA enzyme assayxe2x80x9d and the xe2x80x9cphosphodiesterase [3H] cGMP-SPA enzyme assayxe2x80x9d, supplied by Amersham Life Science, were additionally used for testing. The test was carried out using the experimental protocol specified by the manufacturer. The [3H] cAMP-SPA assay was used for determining the activity of PDE II, with 10xe2x88x926 M cGMP being added to the reaction mixture for the purpose of activating the enzyme. 10xe2x88x927 M calmodulin and 1 xcexcM CaCl2 were added to the reaction mixture for the purpose of measuring PDE I. PDE V was measured using the [3H] cGMP-SPA assay.
In principle, the inhibition of one or more phosphodiesterases of this type leads to an increase in the concentration of cGMP. As a result, the compounds are of interest for all therapies in which an increase in the concentration of cGMP can be assumed to be therapeutic.
The investigation of the cardiovascular effects was carried out on normotensive rats and on SH rats and on dogs. The substances were administered intravenously or orally.
The examination for erection-inducing effects was carried out on conscious rabbits [H. Naganuma, T. Egashira, J. Fuji, Clinical and Experimental Pharmacology and Physiology 20, 177-183 (1993)]. The substances were administered orally or parenterally.
The novel active compounds, and also their physiologically harmless salts (e.g. hydrochlorides, maleates or lactates), can be converted, in a known manner, into the customary formulations, such as tablets, coated tablets, pills, granules, aerosols, syrups, emulsions, suspensions and solutions, using inert, nontoxic, pharmaceutically suitable carrier substances or solvents. In this connection, the therapeutically effective compound should in each case be present at a concentration of from about 0.5 to 90% by weight of the total mixture, i.e. in quantities which are sufficient for achieving the specified dosage range.
The formulations are prepared, for example, by extending the active compounds with solvents and/or carrier substances, where appropriate using emulsifiers and/or dispersants, with it being possible, for example when using water as a diluent, to use organic solvents as auxiliary solvents, where appropriate.
The administration is effected in a customary manner, preferably orally, transdermally or parenterally, for example perlingually, by the buccal route, intravenously, nasally, rectally or by inhalation.
For use in humans, doses of from 0.001 to 50 mg/kg, preferably 0.01 mg/kg-20 mg/kg, are generally administered when administering orally. A dose of 0.001 mg/kg-0.5 mg/kg is expedient when administering parenterally, for example by way of mucosae, nasally, by the buccal route or by inhalation.
Despite this, it can be necessary, where appropriate, to depart from the abovementioned quantities, specifically in dependence on the body weight or the nature of the route of administration, on the individual response to the medicament, on the nature of its formulation and on the time or interval at which the administration takes place. Thus, it can in some cases be sufficient to make do with less than the abovementioned smallest quantity whereas, in other cases, the abovementioned upper limit has to be exceeded. When relatively large quantities are being administered, it may be advisable to divide up these quantities into several individual doses which are given during the course of the day.
The compounds according to the invention are also suitable for use in veterinary medicine. For uses in veterinary medicine, the compounds, or their nontoxic salts, can be administered in a suitable formulation, in accordance with common veterinary procedures. The veterinarian can establish the nature of the application, and the dose, in accordance with the nature of the animal to be treated.
In the following examples of preparing the precursors and end products, it is always necessary, in structural formulae containing one or more unsaturated valences on the nitrogen atom or oxygen atom, to add a hydrogen.
In other words, in structures containing, for example, a structural element xe2x80x9cxe2x80x94Nxe2x80x94xe2x80x9d, what is meant is actually xe2x80x9cxe2x80x94NHxe2x80x94xe2x80x9d, and in structures containing, for example, a structural element xe2x80x9cxe2x80x94Oxe2x80x9d, what is meant is actually xe2x80x9cxe2x80x94OHxe2x80x9d.